As your child with CP is becoming a teenager, there are a couple of things you may want to think about.
The typical cognitive assessments that are used for children require them to be able to use their hands to point to pictures or hold puzzle pieces.
Let me tell you about multimodal communication. We, as typical communicators, all use many different strategies. We use speech, gestures, facial expressions, technology, and no-tech solutions. As communicators, we all size up the situation based upon our communication partners, the context, the environment and then we choose to use the most effective communication strategy.
For a child with CP learning to move, the really important things to remember are that the child should always be active.